Modification of linear rubbery polymers



April 11, 1961 P. G. CARPENTER MODIFICATION OF LINEAR RUBBERY POLYMERS Filed Sept. 50, 1957 ou www. 20.207.592

INVENTOR. P. G. CARPENTER mm-ZOZOE A TTOR/VEVS t processed.

United; States eent MODIFICATION OF LINEAR RUBBERY POLYMERS Paul G. Carpenter, Baton Rouge, La., assignor to Phillips Petroleum Company, a corporation of Delaware Filed sept. 3o, 1951, ser. No. 687,134

' 13 Claims. (Cl. 26o-79) This invention relates to a linear rubbery polymer modified for improved processability and to its method of production. In another aspect this invention relates to a modied polymer of 1,3-butadiene containing a high percentage of cis 1,4 configuration. In one of its more specic aspects this invention relates to a polymer comprising a high percentage of'cs 1,4-polybutadiene moditied for improved processability and to a method of preparing same.' I Natural rubber has certain advantages over synthetic elastomers which make it particularly valuable in the manufacture of truck tire carcasses. One of these properties is low hysteresis which enables natural rubber tire stock to operate aty lower temperatures.l In addition,

ice

v gins -by polymerizing a monomer system comprising a v dride or organo compound of one of the metals alumiconjugated diene having from 4 to 8 carbon atoms in the ypresence of a catalyst system comprising (a) a hynum, gallium, indium, thallium andv beryllium, and (b) a-di, trior tetrahalide of'a group IV metal, such as titanium, silicon, thorium, zirconium', tin, lead, hafnium, germanium, or cerium. v

This process and the polymers formedl therefrom is described in greater detail in the copendingapplication of'Robert P. Zelinski et al., Serial No. 541,033, led October 17, 1955.

The hydride or organo compounds used in these catalyst systems correspond to the general formula MRx, wherein M is one of the metals aluminum, gallium, indium, thallium or beryllium, R is hydrogen, a monovalent saturated acyclic hydrocarbonradical, a monovalent saturated cyclic hydrocarbon radical, a monovalent aromatic hydrocarbon radical or any combination natural rubber is generally superior to synthetic inthe l property of tack which enables plies of natural rubber when placed together to adhere without the use of an adhesive. Improved linear polymers prepared by polymerizing conjugated dienes in the presence of an organo- -metal catalyst system resemble natural rubber in theA properties of tack and low hysteresis. These polymers, however, tend to have'high inherent viscosities thereby making them difficult to process. Polymerization con'- ditions and catalyst amounts can be adjusted to produce polymers of low viscosity; however, this :leads to other diiculties, such aslowered yields.' Y

According to myV invention an improved linear` rubbery polymer having a low inherent viscosity isprovided by polymerizing'conjugate'd dientes in the presence of an organometalV catalyst system, subjecting the polymer while in solution to the oxidizing action ofperoxidic oxygenjby which double bonds are broken and reacting-A the thus formed polymeric -free radicals with a comcis 1,4-polybutadiene, AThe polymers thus formed'have generally lower hysteresis and better tack properties 'than othersynthetic elastomers and' are, inf addition,'quite easily processed, having inherent viscosities considerably lowerthan the unmodied'polymers of the yorganometal catalyzed type.k With thefsamedegreeof cross-linking',

value and processability is increased both beforean'd after milling,

I t is an object of my', invention to provide an improved is linear, Asoluble andeasily Y synthetic elastomer which n is another object df my invention to provide a meth.

od' of modifying-organometal catalyzed polymers ofconjugated die'nes to improve their processabiality. i l l A" further object is to providefa polymer of '.cis lA- Y.

fellowins sesststsnefaarlesen@ idfawie which de I thereof, and wherein x is equal to the valencey of the metal, Le., 2 or 3. Examples of these catalysts which can be used are Al(C2H5)3, A1(CH3)3, HAl(C2H5)2, HzAlCHs, B6(CH3)2, AlHs, G3(C3H7)3, II1(CH3)3, Be(CsH5)z, l1'\1(7C'6H13)3, A1(CH2'-(CH2)1a-CH3)3. Ga(CH5-)3, .In(C6H5)3v andthe like. These polymerization `catalysts can also be used in the form of their known and'stable'organic complexes,`such as complexes with ethers, thioethers, amines, alkalifmetal hydrides, alkali metal alkylsor alkali metal aryls. Examples of such complex vcompounds which can be used as the catalyst 'are LiAlH4, NaAl(CH3)4, NaBe(C6H5)3,

YIn admixture with oneior lmore of the MRx compounds described above, the'catalyst comprises at least one group -manium and cerium. Di, triandtetrachlorides, di, triand tetrabromides, di-, tri-and tetraiodides and di-,tri-

and tetraliuorides of'the'lgroup IV metals can be'usedlin :the catalyst composition either individually or as "mix- .-turesl VThe yterm'group IV.metal vas used herein'is de- Y -ned as Imeaning anyor all of the'foregoing metals, and

v pound containing thethiol group. The process of myy I inventionV is particularly valuable in preparingA modified silicon is denedlas agroup IV) metal for these purposes.

` The tetrahalides of titaniumand zirconium are the pren ferredcom'pounds, with the tetrachlorides and tetraiodides of these vmetals"beingespecially useful because they have a high-activityin the process ofthisinvention.

"the lower the inherent viscosity, the lower. the Mooney Among catalyst compositions which` are preferred are Y the follow-ing: awmixture ot titanium'tetraiodide and trivethylaluminum;4 a mixture of titanium tetraiodide rand tripropylaluminum; a `mixture of ktitaniur'n tetraiodide and l tributylaluminumf; afmi'xture oftitanium tetrachloride and triethylaluminum; and a mixture 'of "ride and triethylaluminum.

'. t f t Y 'Ifile amount ofithe MRx compound yused in these cata-y mols Ptlmo-l of the group IV metal compound. Apreferred ratio, however, from 0.3to 10 molsotthejMRx .4

'te'trahalide'.VVK Increased yields ofl thevvrubbery polymerv are Iozbtavined when usinglafatalyst composition falling within thefpreferred'ratio.- f`

zirconium tetrachloa clude 1,3-butadiene, 2methyl-1,3 butadiene (isoprene), 2,3-dirnethyl-1,3-butadiene, 2-methyl-1,3pentadiene, chloroprene, l-cyanobutadiene, 2,3-dimethyl-1,3-pentadiene, Z-methyl-B-ethyl-1,3-pentadiene, Z-methoxybutadiene, 2- phenylbutadiene, and the lilte. In a preferred process, isoprene is polymerized in the presenceof the catalyst above described to form cis 1,4-polyisoprene` having a chemical structure substantially the same as that of natural rubber. In another preferred process, 1,3- butadiene is polymerizedv in the presence of one of the catalyst systems herein described to form polybutadiene in which an excess of 90 percent of the polymer is formed by 1,4 addition of butadiene.

This invention is applicable tothe polymerization of the above-defined conjugated -dienes eitheralone or in admixture with each other and/ or with, in minor amounts, one or more other compounds 'containing anactive CH2=C group which are copolymerizable therewith, Included among these latter compounds are aliphatic loletins having up to and including 8 carbon atoms per molecule, such as ethylene, propylene, l-butene, l-hexene, and 1octene. Branched chain oletins, such as isobutyl# ene, can be used as well as 1,1-dialkyl-substituted and 1,2 diall-:ylsubstituted ethylenes such as butene-2, pentene- 2, hexene-2, heptene-2, 2methylbutene1, Z-methylhexene-1, Z-ethylheptene-l, and the like. Other olens which can be used include di and polyolens, such as 1,5-hexadiene, 1,4-pentadiene and 1,4,7-octatriene, and cyclic olei'ns, such as cyclohexene. Other examples of compounds containingl an active CH2=C group which are copolymerizable with one or more of the conjugated dienes are styrene, acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, vinyl acetate, vinyl chloride, 2- methyl-S-vinylpyridine, 2-vinylpyridine, 4-vinylpyridine, and the like. Y

As mentioned hereinabove, this invention is applicable to the production of rubbery.. polymers. The term .rublbery polymer includes elastomeric,V vulcanizable Ypolymeric material which after vulcanization, i.e., crosslinking, possesses the properties normally associated with vulcanized rubber, including materials which when compounded and cured exhibit reversible extensibility at 80 F. of over 100 percent of a specimens original length with a retraction of at least 90 percent within one minute after releaserof the stress necessary to elongate to 100 percent. The rubbery polymers produced in accordance with this invention are linear, soluble polymers.

using catalyst compositions falling within these preferred ratios.

The temperature at which the polymerization process is carried out should not exceed 150 C. in order to maintain the degree of gel formation as low as possible. The temperature is generally within the range of 100 C. to 100 C., but it is preferred to operate in the range of about 50 C. to 50 C.- In the formation of cis 1,4- polybutadiene, a temperature range of about 10 C. to 50 C.,is preferred.

The polymerization s preferably carried out intthe presence of an inert, hydrocarbon diluent although the use of such` a diluent is not absolutely necessary. The pressure is generally that sufficient to maintain monomeric material substantially in the liquid phase although higher pressures can be employed, if desired, such as by pressurizing with an inert gas. The catalyst concentration can vary over a wide range and is usually in the soY range of about 0.01 to 15 weight percent or higher, based on the monomeric material charged to the reactor. The preferred catalyst concentration in the production of cis 1,4-polybutadiene is in the range of 0.05 to 10 weight percent and more preferably, between 0.05 and 5 .weight percent based on the 1,3-butadiene charged to the reactor. In general, at the lower mol ratios of trialkylaluminum to titanium tetraiodide, it is frequently desirable to operate above the minimum levelof catalyst concentration.v ,l v

Suitable diluents for use in the polymerization process are parains,` cycloparafnsMand/or aromatic hydrocarbonsV which arerelatively inert, non-deleterious and liquid under' the Ireaction conditions .of the process. The lower molecular weight parans, such as propane, hutane, and

pentane are especial-.ly useful when the process is carried out at4 lowy temperaturesl However, the higher molecular weight parafns and cycloparaflins such as visooctane, cyclohexane, methylcyclohexane and aromatic diluents such 4as benzene, toluene and the like, as well as mixtures ofvthese diluents can also be used. Reactor residence time can vary widely, from 1 second to lhour for Vcontinuous reactions to as long as 24 or moreA hours for batch processes.

The cis 1,4-polybutadiene produced as described possesses physical properties which render it superior in many respectsto conventional synthetic rubbers. Cis 1,4- polybutadiene in vulcanized rubbenstocksshows lower hysteresis than conventional synthetic rubber and also The polymer which is most highly preferred for the i7 practice of my` invention is: cis 1,4-,polybutadiene- [This n.

polymer is prepared by polymerizing 1,3-butadiene substantially as described` above in the presence of aA catalyst system comprising trialkylaluminum and titanium tetraiodide. Polybutadiene thus produced is a rubberypoly- `mery containing as high as90 percent and higher cis 1, 4 addition. Preparation of this polymerl is described more fullyin the copending application of David R. Smith et al., Serial No. 578,166,f`1led April 16, 1956.

The trialkylaluminum employed in thisy preferred catalyst system with titaniuml tetraiodide can be represented by thefformula RgAl, wherein R is an alkyl radicalconltaining'l to 6 carbon atoms. The alkyl groups can be either straight or branched chain alkyls and they can exhibits higher resilience, lower freeze point, greater ease of mill breakdown and higher tensile strength at 200 F., thanvconventional emulsion polymerized polybutadiene.

vAt thecompletion of the polymerization reaction, the reaction mixture is treated to. inactivate thecatalyst, such asby adding an alcohol oru oxidizing agent., If an oxidizingagent is employed fat 4this stage, it is preferred to utilize an amount just sucient to inactivate the catalyst. Howeve'n an excess can be Vemployed and this ,excessV will serve as the source of a portion ofthe peroxidic oxygen 'f inthe oxidizing step of this invention as will be explained be the same or different. For example, suitable alkyls are l IncreasedV yieldsA of the E'polybutadie'rie'product a're obtained -whenY hereinafter. Itis 'then normally desirable toi adjust the concentration ofr polymerjin the dilent to amore dilute solution than that obtained in the polymerization reaction. Concentration of polymer in solution prior to modifying according to my invention is generally in the range of about 0.5 to 10 weightV percentl -'More dilute solutionsrcan be employed if desired, butif the solvent is to be reused in the purification zone, they repurcation problem is thereby increased." HigherY concentrations yield viscous solutions which are Yquite diicult to' handle. A polymer concentration in the range of about; to 7 weight percent is preferred. y v Y The dilute solution of polymer is'uthen contacted with peroxidic roxygen to break double bonds-present 'in thev polymerfthus forming free radicals (which` readilyreact with thethiol -modifyiiig agent. The peroxidicoxygen can be supplied'to the reactionzone in the form of perthiol.

oxides, hydroperoxides, and the like; or the polymer solu-v tion can becontacted with air or other oxygen-containing gases, lthus forming in situ 'polymer hydroperoxides which subsequently decompose under the reaction conditions and act as peroxides which are charged as such. Thiol compound is then added to the solution or can be added simultaneously with the oxidizing agent. Suitable thiol compounds can be represented by the general formula R-S-H, wherein R is selected from the group consisting of alkyl, aryl, alkaryl, arajlkyl, andV theV halogen-substituted alkyl, aryl, alkaryl and aralkyl radicals 'containing from 1-16 carbon atoms. i

Some examples of suitable t'hiols` which can be employed in the Process of this invention are: methyl mercaptan, isopropyl mercaptan, tert-butyl mercaptan, tertdodecyl mercaptan, n-hexadecyl-mercaptan, phenyl mercaptan, benzyl mercaptan, p-xylyl mercaptan, pentachlorothiophenol and IO-phenyldecyl mercaptan.

The amount of R-S-H compound which is used in the process of the present invention can be from 0.0015 to 0.15 gram mols per 100 grams of polymervbeing treated. The amount of material which serves as a source of peroxidic oxygen will depend, of course, on the polymer being treated, the temperature at which the treatment is carried out, and the total A`time which the polymer is subjected to the action of the oxidizing agent and the For example, when a peroxide or hydroperoxide is being employed, the amount of peroxide used will be generally within the range of from 0.002 to 0.033 gram mols per 100 grams or rubbery polymer being treated. If air or other oxygen-containing gas is employed, it is necessary to utilize sufficient amount of gas to form an amount of polymer hydroperoxide within the specified range necessary when peroxides or hydroperoxides are added directly. It is also within the scope of this invention to utilize combinations of these peroxidic oxygen- Vsupplying agents.

When air or other oxygen-containing gas to form the necessary peroxidic `oxygen in situ, the amount of gas employed depends on the temperature and time of the oxidation reaction. The formation of hydroperoxide groups on ya polymer chain takes place at a faster rate at higher temperatures. Air 'or other oxygen containing gas can be bubbled through the polymer solution at a rate within the range between 0.1 and 5 liters of gas per gram of polymer present in the solution. The

` rate of flow of the gas, the total reaction time, and theY desired final inherent viscosity of the polymer are factors which determine the total 'amount of air or `oxygencontaining gas employed. When air or oxygen-containing gas is the sole source of oxygen, an amountbetw'een `is employed v ofreactants is 0.5 part by weightof-triisobutylalurninum, 0.2 part of titanium tetraiodide and 900 parts of benzene per 100 parts by weightof butadiene. After about 15-20 hours reaction time, or when the polymerization has reached the desired level, the solution of rubbery diene polymer is withdrawn from reactor 10 through line 14. A catalyst deactivator such as isopropyl alcohol is added to the system at this point through line 16, thus terminating the polymerization.

Additional dluent (benzene or toluene) is added to the polymer solution in dilution zone 17, the dluent entering by line 18. A dilute solution of polymer in a concentration of about 5 weight percent passes through line 20` to oxidation zone 19. Oxidizing agent is introduced to the oxidation zone through line 21. One suitable oxidizing agent is benzoyl peroxide. The resultant solution is passed to modification zone 22 via line 23. In this em.- bodiment, 4 grams (0.0165 gram mols) of benzoyl peroxide per 100 grams of polymer present in the solution is used to treat the solution in the oxidation zone. Suicient thiol compound is then added to the modification zone through line 24 and combines with the polymer. Consistent with above values, 4 grams (0.029 gram mols) of xylyl rnercaptan per 100 grams of polymer. present is introduced. `Modification zone 22 is provided with suitableheating y,means 26 and thetemperatureis maintained at about'85" C.

After.y the desired reaction drawn from zone 22 through line 27 and a shortstopping agent, such as di-,tert-butyl hydroquinone, is added through line 28 tostop the reaction. The polymerthus treated is passed to further recovery steps, such as prei Vcipitation with 'an excess of a precipitating agent, for example, isopropyl alcohol. The precipitated polymer is recovered, washed and dried by conventional means to yield the nal product of'my invention. By following the above described procedure with the suggested proagents, vuloanization accelerators, reinforcing agents,

45.* with natural rubber and/or rubbery'synthetic polymers 5.0 and 2,500 liters of oxygen per gram of polymer is l:

used.v When air oroxygen-containing gas is used in con-""1 junction with a peroxide, hydroperoxide or the like, an` f amount of gas sufficient to provide as little as 0.1 liter of oxygen per gram of polymer can be employed.

The temperature at which the rubbery polymer is subiected to the action of an oxidizing agentV and-"a thiolcontaining compound can bewithin the range between 25 and 100 C. The time during which the rubbery" polymer is subjected to this action will depend upon the polymer being treated and also upon thev desired nal inherent viscosity of the polymer. The treating'timefwitll ysoftenqetrs, tllers, t' and the like as have been employed can likewise beY compounded with the polymers of my invention. -Elastomer thus produced can be readily fabricated intota number of useful articles, particularly fr applications in which the characteristics of natural rubber are desired.

To furthergillustrate the advantages of myinvention `,the following-.examples are set forth. Reactants,"their v proportions, and other' specific conditions are presented Y as being typical and should not be construed to limit the invention unduly.

y l EXAMPLE I A series vof runs were made iin which 1,3butadiene was .polymerizsd Yto ciSf-lA-plybutadiene and .mod carried out by means of a mercaptan.V These runs were -"according to the. following procedure. f

generally fall-within the` range of from 0.25 to 1'50 hours;`

preferably between 0.5 and 20 hours. y,

r Referring now to the drawing to describe the complete process lof my invention,a schematic operation isY shown which can be either batch o rcontinuous.

throughV line` .117. Apolymerizgation catalyst suohtasvthat resulting, from the, reaction.; of .tliiso,butylalign,inunr and titanium tetra-iodide is fed to the reactor thgh lijnen d n A monomer such A,as A1,3butadiene is fed to rpolymerization zone 10 -The polymerizationjcatalyst in these runscornpris'ed triisobutyl-alurninum and titanium tetraiodide. The devsiredamount of Adluent (toluene in these runs) was added to a one-quart beverage bottle, after which'the desired amount. of triisobutylaluminumwas added to the bottle. Following this charge, the-desired amountloftitanium tetraiodide was `charged yt'o the bottlejand thedesired amount of 1,3v-but'adien'e:wasthen charged; During the chargingjof the; catalyst'cornponentsand the butadienmA 'Y the vapor space'- in the bottle was lcontinuouslyIllushed with nitrogen. Afterthese materials werechar'gedythe 'Y bottle'wassealed withva'neopr'enn'e4 seall adacrow'nfbot* .ttleY capwhichfwas punchedto exposefa portion of lthe neoprene seal.; The bottle was thenlplaced'ifa 309,@-

time has elapsed, for exy ample, about 1.5 hours, the polymer solution is with-v temperature bath and tumbled in this bath for the duration of the polymerization. Y

At the end of the desired polymerization period, an amount of oxygen was injected into the bottle by means of a syringe to deactivate theactive catalyst. An aliquot was withdrawn from the bottle and the polymer in this amount of solution was precipitated by means of isopropyl alcohol. The inherent viscosity -of the polymer was determined. Each bottle in this series of runs contained approximately 20 grams. The reaction mass in each bottle was then diluted to a 4 percent by weight solution of polymer in toluene. Four parts by weight per 100 parts of polymer of benzoyl peroxide was then charged to each bottle, after which two parts, on the same basis, of a 331/3 percent by weight solution of xylyl mercaptan in petroleum oil was charged to each bottle. f The reaction mass was then maintained at 82 C. for 1.5 hours, after which 11/2 percent by weight, based on the monomer originally charged of ditert-butyl hydroquinone was added to the solution. Two percent by weight, based on monomer originally charged, of phenyl-beta-naphthylamine was then added to the solution, after which the polymer was precipitated by contacting the solution with an excess of isopropyl alcohol. The precipitated polymer was then washed with isopropyl alcohol, drained, an'd dried at 60 C. in a 6-1l) were also composited and showed the same yield but'higher inherent viscosity (2.13), gel 27 percent, swelling index of gel 76, 'and Mooney viscosity (ML-4) 116. The appearance of gelin the composited samples indicates that additional crosslinking, probably due to an insuflicieut amount of di-tert-butylhydroquinone employed, occurred after the samples were composited.

EXAMPLE II Two runs were made in which ycis-l4-13'5Plybutadiene, prepared by essentially.. the same polymerization procedure and recipes of the previous examples, was modified by means of a peroxide and a thiol. l

In these runs, two samples of cis-polybutadiene, weighing 40 grams each and containing 2 percent phenylbetanaphthylamine, were each dissolved in 5 liters of benzene. The inherent viscosityiof one of the samples was 9.80, and the inherent viscosity of. the other was 9.28. One-half part by weight per 100 parts of polymer of tertdodecyl mercaptan was added to a portion of each of the solutions. One-half part by weight per 100 parts of polymer of benzoyl peroxide was then added to each portion, and the resulting solution was then maintained at C. over a period of time of several hours. Periodically, samples were taken, and the inherent viscosity was determined.. The results are expressed below as Table II.

vacuum oven. The polymerization recipes for these TABLE n runs are given below, and the results of these runs are expressed below as Table I. sample A sample B Pvlymefizafion recipes "111meat5ofo-, Inherent Time ammo., Inherent hours Viscosity hours Viscosity Parts by Weight 0 (originel) 9. so o (original) 9. 2s 35 1 g2g 1 87g 8.8 D E s. 27 8.52 l 7.20 8.58 Butadiene 10o 100 g- Toluene (purged with N2 at 2 liters/min.). 870 870 4 14 Triisobutylaluxninum (TBA) 0.554 0.693 3' 95 Titanium tetraiedide (TTI) 0. 20S 0. 260 l TBA/TTI mole ratio 7. 5 7. 5 7. '5 Temperature, C 30 30 30 l, Polymerizentmtune, honra.-. 16.5 16.5 16.0 As shownabove, even with relatively small amounts of thiol and oxidizing agent and at lower temperatures, the

TABLE r Modification Toluene Catalyst Inherent Purge Deactiva- Viscosity Run No. Recipe Time, tor Oxy- Betorc Inherent; i Minutes gen, Milli- Modifying Time, Temp., Viscosity moles Hours C. after Moditying l D 1 e 23 5.11 1.0 71 1.24 D 2 23 2 6.' 52 1. o 71 1. 60 E 1v 29 4.72 1.0 71 1.55 E, 2 29 `#3.02 1.0 71 1.24 E 4 29 4561 1.0` 71 1.56. F 2 23 3. 60 0. 5r 71 1. 73 F 2 23 3.02 0.5 71 1.71 F V2y l 23 3.19 0.5 71 1;76 F 2 23 3.57 0.5 71 1. 79 F l2 23 3.38 .0.5 l71 1. 79 Fy 2 l 12V (i)Y 0.5 71 1.09

1 None'of 'the polymers contained gel.

2 In this run, 21.4 miliimoles of dimethylanilne was added alongwith the dl-tert-butyl Y l l hydioquinonc.

8 In this rim, hydroquinone;

i 4 In this run, hydroquinone. n

5 Not measured.

The data of Table 1 shows'the'improvementin polye mer processability rendered by the process of-my invention as evidenced by lowered inherent viscosity.

`Polymer ofl recipes D `and E were-.composited (runs 1-5)and,testedfor processability.4 Yield,.based on total chargewas 94 percentfinherent viscosity 1.82, gel 6 percent,:swelling Vindexbf gel 127,1 and Mooney viscosity (lli/11129125. `Thus the polymer value was enhanced from 13.4Vmi11imoles of dimethylanlline was added along'with the di-tert-butyl y 26.8 muumeieelef aimethyianmne was added :tiene with the arten-butyl modification of inherent viscosity proceeds as a function of time.

EXAMPLE Il ll a fabicationastandpoint. lolymerfof. recipe F. (runs 7.5 cositywas dissolvedinbenzene to forni Ia,st )lutioncoritaining approximately 1 percent rubbery polymer by weight. This solution was divided into several portions, and three series of runs Were made utilizing these portions. In the first series, varying amountvsvof benzoyl peroxide and penta-chlorothiophenol were added to the solution, and the mixture was then maintained at 50 C. The second series was carried out in the same manner as the first, except that xylyl mercaptan, Was the thiol used. The third series used no peroxide, and air was bubbled through the solution of polymer and thiol at the rate of approximately one liter per minute. The results of these runs are expressed below as Table III. Each run employing pentachlorothiophenol, contained 0.83 gram of cis-polybutadiene, while each run in which Xylyl mercaptan was used contained 1.5-grams of the polymer.

TABLE III Parts Thiol/ 100 Parts Benzoyl ture was then placed in` a bottle and maintained at 85 C. while bubbling air through the solution at the rate of approximately one liter per minute.

TABLE v Inherent viscosity after time in hours Inherent Viscosity After Time in Hours l No. 100 Parts Polymer Pentachlorothiophenol l 1 These runs were carried out atroom temperature.

As f a control, the polymer solution (no oxidizer or thiol present) was maintained at C. for several hours with the following results:

' TABLE IVj l v Inherent viscosity after time in hours Inherentlviscosities were Ireduced considerably in a In* the y determination of. yinherent viscosity for `the Y above examplesA the procedureis as follows: The polymer i sample is dissolved in benzeneV from a stainless steel `f screen cage'of special design. l In Veach test, 0.1V gramof relatively short time when benzoyl peroxide was employed as the oxidant and the temperatue'fslightly ele- V vated. Although the resultsjwere producedjrnore slowly,

the air oxidant at room temperature also provedeifecf.

tive when compared with the cotroh vIt caniy bexseen. Y from'the above vdata that a` ivid'e Variety of process vaiiablesY can be chosenk to practice the process of my-invention. *'w l EXAMPLE IV A-sample of cis 1,4-polybutadiene, prepared by'a tri- -.isobutylaluminumetitanium tetraiodide catalyzed'v poly-` Y merization and having an inherent vviscosity of 8.72, was

dissolved in benzene to form a solution `containing0.663- gram of polymer in 200 cubic centimeters of solution... i

Ten cubic centimeters of this solution was withdrawn for the initial viscosity lmeasurement and ten cubicrcenti Y meters was withdrawn at the end of ea'ch hour as Yshovvn polymer and lOOcentimet'ers of benzene are employed.

After stand-ing'I24L-4S hours in benzene,1.thexcage is rell Ymovedand weighed for swelled gel.' The cage is then dried in a vacuum oven maintained ata temperature of -'70-'80C, arid weighed vfor dry;.gel. The gel is calculated 1 ,-asthe weightk per tientv of the -.polyn1er'which is insoluble in benzene.,fTheiswelling index of the gel is determined,v4

as' the weight ratio loffswelled gel to dry gel.. `TheI inherent yviscosity ofi-fthetrubber yis calculated: from the viscosity of the gelfree benzene solution relative to that of pure benzene.'` Therelative viscosity is determined .byV means of Medalia' type viscometers supported in a watergbath which As willbe evident to those skilledin theart, various v modifications of'this inventioncan .be made, orffollowed,

y from the spirit or scope thereof.. p ,l Iclairn: Y'

5f: .f 1. A method of Aprepa'rixrlgfan improved rub'bery ,Amer which comprises forming a diluteigsolution oan l I is maintained at `a temperature of j 4.A method ac cordingto claim 2'wherein .said mono- 1l elastomer prepared by polymerizing a monomer system comprising a major amount 'ofconjugated diene containing from 4 to 8, inclusive, carbon atoms per molecule in the presence of a catalyst system comprising (a) a compound of a metal selected from the group consisting of aluminum, gallium, indium,- thallium and beryllium having the valence linkages thereof individually bound to members selected from the group consisting of hydrogen, saturated acyclic hydrocarbon radicals, saturated cyclic hydrocarbon radicals, and aromatic hydrocarbon radicals `and alkali metal hydride, alkali metal alkyl and alkali metal aryl complexes of said compound of a metal and (b) a halide of a group IV metal; treating said solution with an oxidizing agent selected from the group consisting of peroxides, hydroperoxides, oxygen containing gases and mixtures thereof and immediately contacting in a ratio of 100 grams of the polymer withirom 0.0015 to. 0.15 gram mols of a compound having the general formula R-S-H wherein R is selected from the group consisting of alkyl, aryl, alkaryl and halogen-substituted alkyl, aryl, alkaryl, and aralkyl radicals containing from 6. A method of modifying an improved rubbery polymerrwhichhas been preparedby polymerizing 1,3-butadiene-.in an inert diluent in the'presence of a catalyst system "comprising trialkylalurninum wherein the alkyl radical contains from 1 to 6, inclusive, carbon atoms and titanium tetraiodide, thereby forming a linear polymer of predominately cis 1,4-conguration, which comprises subjecting said linear polymer in an 0.5 to weight percent solution to the action of an oxidizing agent selected from the group consisting of peroxides, hydroperoxides, oxygen containing gases and mixtures thereof in a ratio equivalent to 0.002 to ,0.33 gram molsof peroxide per 100 grams of polymer, immediately contacting the thus oxidized polymer with a thiolpcompound having the general formula R-S-H wherein R is selected from the group consisting of alkyl, aryl, alkaryl, and halogensubstituted alkyl, `aryl, alkaryl and aralkylradicals con- 1 to 16 carbon atoms, said contacting being conductedV within a temperature range of to 100 C. for from 0.25 to 150 hours; and recovering the thus modified polymer from solution.

2. A method of modifying an improved rubbery polymer which has been prepared by polymerizing in solu-Y tion a monomer system comprisinga major amount of conjugated diene containing from 4 to 8, inclusive, carbon atoms per molecule in the presence of a catalyst system comprising (a) a compound of ametal selectede from the group consisting of aluminum, gallium, indium.:

thallium and beryllium having the valence linkages thereof individually bound to members selected from the* group consisting of hydrogen, saturated acyclic hydrocarbon radicals, saturated cyclicn hydrocarbon radicals,

and aromatic hydrocarbon radicals and alkali metal taining from l to 16 carbon atoms in a ratio of 0.0015 to 0.15 gram mols of said R--S--H compound per 100 grams of polymer, saidv contacting being conducted within a temperature range of 25 to 100 F. for from 0.25 to 150 hours, and precipitating the thus modified polymer.Y

7. A method according to claim 6 wherein said thiol compound is xylyl mercaptan.

8. A method according to claim 6 wherein said thiol compound is tert-dodecyl mercaptan.

9. A method according to claim 6 wherein said thiol Ycompound is penta-chlorothiophenol.

10. A method according to claim 6 wherein said oxidizing agent is benzoyl peroxide.

11. A method according to claim 6 wherein said oxi- 1, dizing agent is air.

12. A polymer prepared by the method of claim 6.VV

' 13. A method of modifying an improved rubbery polymer which vhas been prepared by polymerizing 1,3-butadiene in an inert hydrocarbon diluent in the presence of a catalyst system consisting essentially of from 1.5 to 10 hydride, alkali metal alkyl and alkali metal aryl complexes of said compound of a metal and (b) a halide of a group IV metal, at a temperature inthe range'of 100 C. 100 C. to form a rubbery, linear polymer, which comprises deactivating the catalyst, diluting the solution to a polymer concentration of about 0.5 to 10 weightv percent, subjecting said polymer to the action of an oxidizingagent selected from the group consisting of peroxides, hydroperoxides, oxygenV containing gase'siand mixtures thereof ina ratio equivalent to from" 0.002 to 0.3.3 .gram mols of peroxide per 100 grams .of polymer, immediately contacting the oxidized polymer-with a compound having the general formula .R-S-H` wherein Ris selected from the group consisting, of alkyl, aryl, alkaryl, and halogen-substituted alkyl, aryl, alkaryl'and aralkyl radicals containingfrom A1 to 16 carbon atoms,

in a ratio of 0.0015 to 0.15 gram mols of said RS-H 1 compound .per v100 ..gramsof polymer, saidcontacting being conducted within a temperature" range of 25 to 100 F. for from 0.25 to 150 hours and precipitating the thus modified polymer. i 1 I 3.A- method according to `claim 2 wherein sai'drrionomer system consists essentially of 1,3-butadiene'.

mer system consists essentiallyofisopre.

5. A polymer prepared by the method of claim 2.

m-ols of triisobuylaluminum" per mol Vof titanium tetraiodide, said catalyst being present in an amount of about 0.05 to 10 weight percent based on the monomer charged,

at a temperature in the range of about l0 to 50 C., thus Vvfforming cis V1,4-polybutadiene, which comprises inactivating the catalyst, adjusting the concentration of polymer in Solution toy about 2 to 7 weight percent, treating the polybutadiene with an yoxidizing agent selected from the `group consistingv of peroxides, hydroperoxides, oxygen containing gases and mixtures .thereof in a ratio equivalent to about 0.002 to 0.33. gram mols of peroxide per grams of polymer, immediately subjecting said polybutadiene to vreaction with a thiol compound having the general formula R-S;H wherein R is selected from the group consistingof alkyl, aryl, alkaryl, and halogensubstituted alkyl, aryl, alkaryl and aralkyl radicals'containing from 1 to 16 carbon atoms in a ratio of 0.0015 to 0.15 gram mols of said R-S-H compound per 100 grams of polymer, at a temperature in the range of about 25 to 100`C.. for about 0.5 to 20 hours, and precipitating the vthus modied polymer.

- Refeiences Cited in the le of this patent UNITED STATES'PATENTS 2,660,563 "Baneset al. `z` g Nov. 24, 1953 2,832,759l Nowlinet al Apr. 29, 19i58 

2. A METHOD OF MODIFYING AN IMPROVED RUBBERY POLYMER WHICH HAS BEEN PREPARED BY POLYMERIZING IN SOLUTION A MONOMER SYSTEM COMPRISING A MAJOR AMOUNT OF CONJUGATED DIENE CONTAINING FROM 4 TO 8, INCLUSIVE, CARBON ATOMS PER MOLECULE IN THE PRESENCE OF A CATALYST SYSTEM COMPRISING (A) A COMPOUND OF A METAL SELECTED FROM THE GROUP CONSISTING OF ALUMINUM, GALLIUM, INDIUM, THALLIUM AND BERYLLIUM HAVING THE VALENCE LINKAGES THEREOF INDIVIDUALLY BOUND TO MEMBERS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, SATURATED ACYCLIC HYDROCARBON RADICALS, SATURATED CYCLIC HYDROCARBON RADICALS, AND AROMATIC HYDROCARBON RADICALS AND ALKALI METAL HYDRIDE, ALKALI METAL ALKYL AND ALKALI METAL ARYL COMPLEXES OF SAID COMPOUND OF A METAL AND (B) A HALIDE OF A GROUP IV METAL, AT A TEMPERATURE IN THE RANGE OF -100* C. 100*C. TO FORM A RUBBERY, LINEAR POLYMER, WHICH COMPRISES DEACTIVATING THE CATALYST, DILUTING THE SOLUTION TO A POLYMER CONCENTRATION OF ABOUT 0.5 TO 10 WEIGHT PERCENT, SUBJECTING SAID POLYMER TO THE ACTION OF AN OXIDIZING AGENT SELECTED FROM THE GROUP CONSISTING OF PEROXIDES, HYDROPEROXIDES, OXYGEN CONTAINING GASES AND MIXTURES THEREOF IN A RATIO EQUIVALENT TO FROM 0.002 TO 0.33 GRAM MOLS OF PEROXIDE PER 100 GRAMS OF POLYMER, IMMEDIATELY CONTACTING THE OXIDIZED POLYMER WITH A COMPOUND HAVING THE GENERAL FORMULA R-S-H WHEREIN R IS SELECTED FROM THE GROUP CONSISTING OF ALKYL, ARYL, ALKARYL, AND HALOGEN-SUBSTITUTED ALKYL, ARYL, ALKARYL AND ARALKYL RADICALS CONTAINING FROM 1 TO 16 CARBON ATOMS, IN A RATIO OF 0.0015 TO 0.15 GRAM MOLS OF SAID R-S-H COMPOUND PER 100 GRAMS OF POLYMER, SAID CONTACTING BEING CONDUCTED WITH A TEMPERATURE RANGE OF 25 TO 100*F. FOR FROM 0.25 TO 150 HOURS AND PRECIPITATING THE THUS MODIFIED POLYMER. 